I recently purchased a Zenith ZHX-313 Home Theatre-in-a-Box and have been happy with it so far. I've used some of speakers as the front left/right and as the back speakers. The other day, I tried to show my friend a DVD on it and I noticed that there was no sound but instead this constant beating sound as if it was a faint hearbeat. I suspected that there may be some crossed cables and that I was getting feedback, but I found no such problems. Is my receiver bad or what? Hopefully someone can help because I'm pretty new to the whole audio thing.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic